Multiple blood bags are commercially available from the Fenwal Division of Baxter Travenol Laboratories, Inc. for collecting and processing blood under sterile conditions, to obtain various blood components that may be desired, for example, packed red cells, plasma, platelets, and cryoprecipitate.
The currently-available blood bags are made of a polyvinyl chloride formulation which includes, as an ester-type plasticizer, di-2-ethylhexylphthalate. Such a plasticizer is absolutely necessary for polyvinyl chloride formulations, since polyvinyl chloride itself is not a suitable flexible plastic material for use as a container. Such blood bags have served extremely well in the storage and processing of blood and blood components, exhibiting a high survival rate with a low plasma hemoglobin content after, for example, 21 days of storage.
Other chlorine-free plastic formulations have been tested as candidate blood bag materials as well, including flexible polyesters, polyolefins, and the like. Surprisingly, many of the materials tested, while giving indications of being good plastic materials for the manufacture of blood bags, have caused blood stored in containers made of such materials under the usual blood storage conditions to exhibit an undesirably high plasma hemoglobin content after, for example, 21 days of storage, indicating that the lysis rate of the red blood cells is high.
In accordance with this invention, it has been surprisingly found that the presence of certain ester-type plasticizers such as di-2-ethylhexylphthalate and di-2-ethylhexyladipate in various chlorine-free plastics which do not normally contain such plasticizers causes a significant lowering of the plasma hemoglobin content during long-term storage of blood in containers made of such plastic, when compared with containers made of similar plastic materials which are free of the ester-type plasticizers. This can be used to provide blood bags and other blood-contacting medical devices which are made out of chlorine-free plastic entities, having different advantages and properties as may be desired, but which nevertheless exhibit a similar desirably low blood hemolysis rate during long-term storage to that presently available in commercial polyvinyl chloride formulations.